Electric control apparatus for fuel burners



Feb. 18, 1936. A. L. RUBEL 2,030,941

ELECTRIC CONTROL APPARATUS FORFUEL BURNRS Original Filed Aug. 15, 1932 Patented Feb. 18, 1936 UNITED STATESA PATENT OFFICE atacan ELECTRIC CONTROL APPARATUS Fon FUEL BUaNEas Abraham L. Rubel, Des Moines, Iowa, assignor to Penn Electric Switch Co., Des Moines, Iowa, a

corporation of Iowa Original application August 15, 1932, Serial No.

628,883. Divided and this application December 31, 1934, Serial No. 759,964

' 2 claims. (ci. 15s-za) including a warp switch which is energized after combustion occurs in order to break the circuit through the heater of a safety switch, so that upon combustion occurring and being maintained, the safety switch will not trip out.

Still a further object is to provide a controlfor the burner so arranged that upon combustion failure a purging period is provided by the slow cooling down of a warp switch and contacts of the warp switch are re-engaged after such cooling down so that the control apparatus is re-cycled for further automatic operation.

Still a further object is to provide control apparatus including a relay which initiates and terminates operation of a fuel burner and which initiates operation of ignition mechanism for the fuel burner, termination of the operation of the ignition mechanism being eected by combustion occurring. Y

Still a further object is to provide a control apparatus in which a safety switch heater, a warp switch and a relay are all in circuit with each other, a combustion responsive switch being effective to .close the heater for the warp switch, which upon becoming heated will open the c ircuit through the safety switch heater so that upon combustion failure the warp switch heater will be de-energized and, after slowly cooling down, the warp switch will close for re-initiating operation of the burner, the delay period of time during which the warp switch heater cools down being of such length as to provide a purging period for the burner. a fuel burner so that upon combustion failure occurring, such as caused by a down draft in the furnace, a slug of water in the fuel oil or the like, automatic operation of the apparatus will recycle the burner after afpurging period has been provided to allow the draft of the furnace to purge the combustion chamber of any exposed gases caused by the introduction of fuel after combusi tion fails.

The apparatus is used on' and combination of the various parts of my device, whereby the objects contemplated are attained, as hereinafter more fully set forth, pointed out in my claims, and illustrated in the accompanying drawing, in which:

Figure 1. is an electrical diagrammatic View showing the circuit for my purging type of control apparatus for fuel burners.

Figure 2 is a simplified diagrammatic view prdvided to facilitate tracing the various circuits through theI elements of the apparatus.

On the accompanying drawing I have used the reference numeral I0 to indicate a line switch. A limit switch is shown at I2, which may be temperature or steam pressure operated and which is ordinarily used in control circuits of furnaces and boilers to prevent the furnace or boiler being heated to an excessive degree. Junction boxes are shown at i4 and I6.` These form no essential part of my present invention, but are merely provided for the convenience of the electrician when installing or wiring the apparatus. The junction box I6has terminals indicated at I, 2, 3 and 4.

My apparatus further includes a room thermostat I8, a. combustion responsive control switch 20, an ignition switch 22, also responsive to combustion, a safety switch 24, a warpswitch 26 and a relay 28. The relay 28 includes'an armature 28a to be attracted by energization of the relay. At 30 a furnace is shown and the burner 30 therefor is shown more or less diagrammatically An ignition transformer is shown at 34 and a spark gap at 36. This comprises the ignition mechanism mentioned in some of my claims.

Thel control switch 20 has contacts 38, 4I and 42. The contacts 38 and 4I may be termed first contacts closed in the presence of combustion while the contacts 38 and 42 may be termed .sec ond contacts closed in the presence of combus- 40 tion. The ignition switch 22 hasv contacts 44 and 46 closed in the absence of combustion.

The safety switch 24 has contacts 48 and 50. The safety switch includes a heater 52 and a bimetal latch 54 which when warped to the dotted 45 line position of Figure 1 by heat from the heater 52 will permit disengagement of the contacts 48 and 50. The warp switch 26 includes contacts 56 and 60 and a bi-metal actuator 62 for the contacts 56. A heater 64 is provided for warping the bi- 50 metal actuator 62 to open the contacts 56 and 60 when the bi-metal element 62 warps due to the l action of the heater 64.

The relay 28 has burner control-.contacts 66 .and 68 and holding contacts l0 and 12. The control and ignition switches 20 and 22 are normally in the solid line positions. Upon combustion occurring, a bi-metal helix 2| causes movement of the contacts 38 and 46 to their dotted line positions. The combustion responsive switches 20'- and 22 are oi the ordinary type commonly termed a stackswitc having a slip connection to cause immediate movement of the movable contacts from one'posi'tionto another and thereafter permit slippage.

The warp switch 26 when heated by energization of the heater 64 warps to the dotted line position of Figure 1. In conjunction with my apparatus, I provide a transformer 14 having a primary winding 16 and a secondary low voltage winding 18 so that the relay mechanism for controlling it need not be constructed for, high voltage current.

Practical operation Closing of the contacts in the room thermostat engages the contact l2for establishing a 2nd energization of the relay.

4ergizing the warp swi circuit through the warp switch heater 64 to cause the warp switch to warp to its dotted line position. This opens the circuit through the safety switch heater 52.

Combustion establishment also closes the circuit through contacts 38 and 4| to establish a "3rd or holding circuit through the contacts lil and 12 of the relay which?A have been engaged by Upon combustion failure the contact 38 separates from the contacts ll and 42, thus de-enheater 6I and de-energizing the holding or 3rd circuit through the contacts 10 and .12 for terminating operation of the burner V,M32 b y separation of the contacts 66 and 68. 'I'liyereaiter-V the heater 6l will gradually cool down and so will the bi-metal element 62 of the warp switch 26. It will iinally assume a position re-engaging the contacts 56 and 60 which re-establish the ist circuit through the relay coil to re-cycie the apparatus by re-initiatng operation ofthe burner 32. The period oi time during which the bi-metal element 62 moves from the dotted line position to the full line position of Figure 1 provides a period during which the furnace is purged of. gases which might explode when the contacts 66 and 68 are re-engaged to re-establish ignition as well as re-initiate operation of the bru'ner.

` The warp switch operates the safety switch heater circuit and controls the main circuit so that a purging period may be provided after which the operation of the burner is re-initiated and the heater 52 of the safety switch is energized so asl to guard against combustion not occurring by opening'the main circuit after a period of time suilicient to permit combustion to occur if the controller is in proper condition for operation. I1' there is any condition present which will not allow combustion to occur, then the contacts 48 and 50 are separated after the time period mentioned, whereupon the trouble must be remedied and the safety switch thereafter reset manually for again placmg the burner in operation.

AlthoughI have shown the transformer 14 it will be obvious that my apparatus maybe operated by high voltage current and the transformer. omitted. A change of this character and others may be made in the construction and arrangement of the parts of my device without departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims any modified forms of structure or use of mechanical equivalents which may b`e reasonably included within theirl scope.

I claim as my invention:

1. In combination with an electrically operated fuel burner, a control system comprising a relay having an actuating winding, a holding winding and holding contacts operable when the actuating winding is energized to close the burner circuit to initiate operation, a room thermostat controlling energization of said relay, a thermal time limit cut out switch controlling said system and including a resistance heater, a warp switch haviiig'a warp element, a heater and contacts which are closed when said element is cold and open when said elementis heated, combustion responsive means having iirst and second contacts closed in the presence of combustion, a iirst circuit including in series said room thermostat, said cut out switch heater, said contacts oi said warp switch and said actuating winding, a second circuit shunting said cut out switch heater, said contacts of said rwarp switch and said relay and'including in series the rst contacts of said combustion switching means and the heater for said warp element and athird circuit in parallel with the heater for said warp element and including in series said second contacts of the combustion responsive switching means, said holding contacts and said holding winding, said warp element moving slowly when cooling .due to deenergization of its heater caused by combustion failure opening said rst set of contacts of said combustion switching means whereby a purging period is provided between the de-energization of said relay caused by combustion failure opening said second contacts oi said combustiony switch to stop operation oi' said burner and reengagement oi' the contacts of said warp switch to re-initiate operation of the burner by re-establishing said iirst circuit.

2. In combination with an electrically operated fuel burner and its ignition mechanism, a control system comprising a relay having an actuating winding, a holding winding and holding contacts operable when the actuating winding is energized to close the burner circuit to initiate operation, a room thermostat controlling energization of said relay, a thermal time limit cutout switch controlling said system and including a resistance heater, a warp switch having a warp element, a heater and contacts which 'are closed when said element is cold and open when said element is heated, combustion responsive means having iirst and second contacts closed in the resence of combustion and third contacts opened in' the presence of combustion and connected in series with said ignition mechanism, arst circuit including in series said room thermostat, said cut out switch heater, said contacts of said warp switch and said actuating winding, a second circuit shunting said cutout switch heater, said contacts of said warp switch and said relay and including' in series the iirst contacts of for said warp element and a third circuit in pasallel with the heater for said warp element and including in series said second contacts o! the combustion responsive switching means. said holding contacts and said holding winding. Nid

warp element moving slowly when cooling due l to de-energization o! its heater caused by oombustionfailure opening said rst set of contacts of said combustion switching means whereby a purging period is provided between the de-enerv gization of said relay caused by combustion tailure opening said second contacts of said combustion switch to stop operation oi said burner and re-engagement oi' the contacts of said warp switch to re-initiate operation of the burner by re-establlshing Bald rst circuit.

ABRAHAM L. RUBEL. 

